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<html>
  <head>
    <meta charset='utf-8'>
    <meta name='viewport' content='width=device-width, initial-scale=1, user-scalable=no'>
    <meta name='mobile-web-app-capable' content='yes'>
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    <!-- Origin Trial Token, feature = WebXR Device API, origin = https://immersive-web.github.io, expires = 2018-08-28 -->
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    <title>Spectator Mode</title>

    <link href='css/common.css' rel='stylesheet'></link>

    <!--The polyfill is not needed for browser that have native API support,
        but is linked by these samples for wider compatibility.-->
    <!--script src='https://cdn.jsdelivr.net/npm/webxr-polyfill@latest/build/webxr-polyfill.js'></script-->
    <script src='js/xrray-polyfill.js' type='module'></script>
    <script src='js/webxr-polyfill.js'></script>

    <script src='js/webxr-button.js'></script>
  </head>
  <body>
    <header>
      <details open>
        <summary>Spectator Mode</summary>
        <p>
          This sample demonstrates how to render a separate, 3rd person view of
          the scene to an external monitor if one is available. This sample is
          not applicable to mobile or standalone devices.
          <a class="back" href="./index.html">Back</a>
        </p>
      </details>
    </header>
    <main style='text-align: center;'>
    </main>
    <script type="module">
      import {Scene} from './js/cottontail/src/scenes/scene.js';
      import {Renderer, createWebGLContext} from './js/cottontail/src/core/renderer.js';
      import {Gltf2Node} from './js/cottontail/src/nodes/gltf2.js';
      import {QueryArgs} from './js/cottontail/src/util/query-args.js';
      import {FallbackHelper} from './js/cottontail/src/util/fallback-helper.js';
      import {mat4} from './js/cottontail/src/math/gl-matrix.js';

      // If requested, initialize the WebXR polyfill
      if (QueryArgs.getBool('allowPolyfill', false)) {
        var polyfill = new WebXRPolyfill();
      }

      // XR globals.
      let xrButton = null;
      let xrImmersiveRefSpace = null;
      let xrNonImmersiveRefSpace = null;

      // WebGL scene globals.
      let gl = null;
      let renderer = null;
      let scene = new Scene();
      scene.addNode(new Gltf2Node({url: '../media/gltf/garage/garage.gltf'}));
      scene.standingStats(true);

      // Indicates if we are currently presenting a spectator view of the
      // scene to an external display.
      let spectatorMode = false;
      let spectatorButton = null;
      let spectatorProjectionMatrix = mat4.create();
      let spectatorViewMatrix = mat4.create();
      let headset = null;

      let mainElement = document.querySelector('main');

      function initXR() {
        xrButton = new XRDeviceButton({
          onRequestSession: onRequestSession,
          onEndSession: onEndSession,
          supportedSessionTypes: ['immersive-vr']
        });
        document.querySelector('header').appendChild(xrButton.domElement);

        if (navigator.xr) {
          requestInlineSession()
          .then((session) => {
            gl.canvas.addEventListener('touchend', () => {
              session.end().then(() => {
                requestInlineSession({ optionalFeatures: ['local-floor'] });
              })
            }, { once: true });
          });
        } else {
          initFallback();
        }
      }

      function initFallback() {
        initGL();
        let fallbackHelper = new FallbackHelper(scene, gl);
        fallbackHelper.emulateStage = true;
      }

      function initGL() {
        if (gl)
          return;

        gl = createWebGLContext({
          xrCompatible: true
        });

        function onResize () {
          gl.canvas.width = (gl.canvas.offsetWidth * window.devicePixelRatio);
          gl.canvas.height = (gl.canvas.offsetHeight * window.devicePixelRatio);
        }
        window.addEventListener('resize', onResize);
        onResize();

        renderer = new Renderer(gl);
        scene.setRenderer(renderer);
        scene.inputRenderer.setControllerMesh(new Gltf2Node({url: '../media/gltf/controller/controller.gltf'}));

        // Because we may be rendering to the gl context's backbuffer now we
        // need to start monitoring resize events to manage it's size.
        window.addEventListener('resize', onResize);
      }

      function onRequestSession() {
        navigator.xr.requestSession('immersive-vr', {requiredFeatures: ['local-floor']})
        .then((session) => {
          session.mode = 'immersive-vr';
          xrButton.setSession(session);
          onSessionStarted(session);

          // When the exclusive session starts, add a button to the page that
          // users can click to start the spectator mode. It's important to not
          // begin presenting spectator mode right away, because on some devices
          // that may mean doing additional work that the user can't see. By
          // requiring a button click first you're ensuring that the user CAN
          // still access the 2D page somehow.
          spectatorButton = document.createElement('button');
          spectatorButton.innerHTML = 'Enable spectator mode';
          spectatorButton.addEventListener('click', onEnableSpectatorMode);
          mainElement.appendChild(spectatorButton);
        });
      }

      function requestInlineSession(options) {
        return navigator.xr.requestSession('inline', options)
          .then((session) => {
            session.mode = 'inline';
            return onSessionStarted(session);
          });
      }

      function onSessionStarted(session) {
        session.addEventListener('end', onSessionEnded);

        initGL();

        session.updateRenderState({
          baseLayer: new XRWebGLLayer(session, gl)
        });

        session.requestReferenceSpace('local-floor').then((refSpace) => {
          return refSpace;
        }, (e) => {
          if (!session.mode.startsWith('immersive')) {
            // If we're in inline mode, our underlying platform may not support
            // the stationary reference space, but an identity space is guaranteed.
            return session.requestReferenceSpace('viewer');
          } else {
            throw e;
          }
        }).then((refSpace) => {
          if (session.mode.startsWith('immersive')) {
            xrImmersiveRefSpace = refSpace;
          } else {
            xrNonImmersiveRefSpace = refSpace;
          }

          session.requestAnimationFrame(onXRFrame);
        });

        return session;
      }

      function onEndSession(session) {
        session.end();
      }

      function onSessionEnded(event) {
        if (event.session.mode.startsWith('immersive')) {
          xrButton.setSession(null);

          // When we exit the exclusive session, stop presenting the spectator
          // view and remove the WebGL canvas from the document.
          if (spectatorMode) {
            spectatorMode = false;
            document.body.removeChild(gl.canvas);
          }

          // Remove the spectator button if needed.
          if (spectatorButton) {
            mainElement.removeChild(spectatorButton);
            spectatorButton = null;
          }

          // Show the inline session's canvas again.
          gl.canvas.style.display = '';
        }
      }

      // Called when the user clicks the button to enable spectator mode.
      function onEnableSpectatorMode() {
        spectatorMode = true;

        // Append the WebGL context's canvas to the page so that we can render
        // directly to it.
        document.body.appendChild(gl.canvas);
        onResize();

        // Remove the spectator button, since it's no longer needed. You could
        // alternately change the button's function to disable spectator mode.
        if (spectatorButton) {
          mainElement.removeChild(spectatorButton);
          spectatorButton = null;
        }

        // Load up a mesh that we can use to visualize the headset's pose.
        if (!headset) {
          headset = new Gltf2Node({url: '../media/gltf/headset/headset.gltf'});
          scene.addNode(headset);
        }
      }

      function onResize () {
        if (spectatorMode) {
          // The spectator view does take time to render, and can impact the
          // performance of the in-headset view. To help mitigate that, we'll
          // draw the spectator view at half the native resolution.
          gl.canvas.width = (gl.canvas.offsetWidth * window.devicePixelRatio) / 2.0;
          gl.canvas.height = (gl.canvas.offsetHeight * window.devicePixelRatio) / 2.0;
        }
      }

      function onXRFrame(t, frame) {
        let session = frame.session;
        let refSpace = session.mode.startsWith('immersive') ?
                         xrImmersiveRefSpace :
                         xrNonImmersiveRefSpace;
        let pose = frame.getViewerPose(refSpace);

        scene.startFrame();

        session.requestAnimationFrame(onXRFrame);

        scene.updateInputSources(frame, refSpace);

        scene.drawXRFrame(frame, pose);

        // If spectator mode is active, draw a 3rd person view of the scene to
        // the WebGL context's default backbuffer.
        if (spectatorMode) {
          // Bind the WebGL context's default framebuffer, so that the rendered
          // content shows up in the canvas element.
          gl.bindFramebuffer(gl.FRAMEBUFFER, null);

          // Clear the framebuffer
          gl.clear(gl.COLOR_BUFFER_BIT | gl.DEPTH_BUFFER_BIT);

          // Set the viewport to the whole canvas
          gl.viewport(0, 0, gl.drawingBufferWidth, gl.drawingBufferHeight);

          // Set up a sensible projection matrix for the canvas
          mat4.perspective(spectatorProjectionMatrix, Math.PI*0.4, gl.drawingBufferWidth / gl.drawingBufferHeight, session.renderState.depthNear, session.renderState.depthFar);

          // Set up a view matrix that gives us a 3rd-person view of the scene.
          // In this case it's positioned in a corner of the garage scene near
          // near the ceiling and looking down at the user.
          mat4.identity(spectatorViewMatrix);
          mat4.translate(spectatorViewMatrix, spectatorViewMatrix, [-1.75, 2.0, 1.75]);
          mat4.rotateY(spectatorViewMatrix, spectatorViewMatrix, Math.PI * -0.25);
          mat4.rotateX(spectatorViewMatrix, spectatorViewMatrix, Math.PI * -0.15);
          mat4.invert(spectatorViewMatrix, spectatorViewMatrix);

          // Update the headset's pose to match the user's and make it visible
          // for this draw.
          if (headset) {
            headset.visible = true;
            headset.matrix = pose.transform.matrix;
          }

          // Draw the spectator view of the scene.
          scene.draw(spectatorProjectionMatrix, spectatorViewMatrix);

          // Ensure the headset isn't visible in the VR view.
          if (headset) {
            headset.visible = false;
          }
        }

        scene.endFrame();
      }

      // Start the XR application.
      initXR();
    </script>
  </body>
</html>
